The main goal of our proposed research is to integrate an on-line immunodetection with capillary electrophoresis for multiresidue analysis of structurally related drugs and their metabolites in body fluids. Capillary immunophoresis as a hybrid analytical technique exhibits the analytical power of electrophoretic separation and immunoselectivity for the identification and quantification of trace amounts of therapeutic drugs in complex sample matrices. In analogy to a two-dimensional separation system, capillary electrophoresis as the first dimension, resolves drug analytes based on differences in their size, electrical charge, and hydrophobicity. Immunoreaction, as the second dimension of separation utilizes the antibody's cross-reactivity for the recognition of drug analytes with a common structural element (epitope). To achieve our research goal, three technical features of capillary immunophoresis have to be addressed: (i) the selection of separation mode and the effect of electroosmotic control on the separation resolution of drug analytes in capillary electrophoresis (ii) the quantitative dependence of applied electric field strengths capillary dimensions, and solution ionic strengths on the effectiveness of analyte transfer and mixing of drug analytes with antibodies in a post-capillary immunoreactor, and (iii) the direct sensing of the antigen (drug analyte)-antibody reaction by monitoring the fluorescence polarization of the hapten- fluorescein conjugate (tracer) in a competitive immunoassay format. To further simplify the drug monitoring procedures and reduce health-related costs, our long-term objective is to demonstrate the potential of capillary immunophoresis for the simultaneous detection of several commonly abused or therapeutic drugs in a single biological fluid sample. Capillary immunophoresis as a revolutionary method for therapeutic drug monitoring shows significant promise for quantum jumps in selectivity, sensitivity, and speed over the current analytical methods. The development of capillary immunophoresis and its success relies on establishing many technical milestones in diverse fields including those outlined in this project as well as the future integration of micromachining and array detection techniques.